Pressure pulse cleaning for adsorption tower distributors

ABSTRACT

An on-line method and apparatus for dislodging deposits from the distributors (12) in an adsorption tower (10) thereby cleaning the tower (10) by causing a surge in a fluid to dislodge the blocked openings (14) of the distributors (12).

This is a division of application Ser. No. 07,809,377 filed Dec. 18,1991 now U.S. Pat. No. 5,259,446.

FIELD OF THE INVENTION

The present invention relates in general to cleaning an adsorptiontower, and more particularly to pressure pulse cleaning an adsorptiontower to dislodge deposits from the distributors.

DESCRIPTION OF THE RELATED ART

Adsorption towers are devices known in the art to distill, refine orseparate liquids. One such application is the upgrading of heavy water(D₂ O) for nuclear power plants. FIG. 1 is a schematic diagram of asectional view of such an adsorption tower. The tower (10) contains aplurality of distributors (12) oriented in a vertical arrangement. Eachdistributor (12) is essentially a large sprinkler with as many as fourhundred 1/16 inch holes or openings (14) located on the bottom of tubes(16) extending out of the distributor (12), as best seen in FIG. 2. Theheavy water descends through the tower (10) passing through eachdistributor (12) via the openings (14). A packing or heating coil (15)is ordinarily positioned under the distributor for filtering or heatingin a known manner. Normally a liquid vapor such as H₂ O vapor in theexample also enters the tower (10).

The problem with these devices is that the openings (14) in thedistributors (12) become blocked over time from deposits carried by theliquid rendering the adsorption tower (10) ineffective in its function.

Currently, these towers have to be shut down and dismantled with all ofthe distributors being removed and then physically cleaned. Each opening(14) is cleaned one at a time. After cleaning, the distributors (12) arethen reassembled in the towers (10).

In a nuclear generating station, shut downs may occur twice a year for aduration of six to eight weeks for cleaning the distributors. The shutdowns are costly and cause radiation exposure to the workers as well asthe environment.

U.S. Pat. No. 5,006,304 discloses a method for loosening and removingsludge and debris from a nuclear steam generator by submerging a lowerportion in water and then generating a succession of shock waves in thewater by means of pulses of a pressurized gas. The disclosed methodrequires the operation to be shut down during cleaning. Related patentsdisclosing similar subject matter include U.S. Pat. Nos. 5,019,329,4,899,697 and 4,921,662.

U.S. Pat. No. 4,773,357 describes a method of cleaning the tube sheet ofa heat exchanger by utilizing a water cannon for explosively discharginga quantity of water from the muzzle to dislodge sludge from the tubesheet of the heat exchanger. U.S. Pat. No. 4,905,900 describes a similarmethod.

Thus, there is a need for a method of cleaning distributors in anadsorption tower which may be used on-line without interrupting theoperation of the tower to eliminate shutdowns. This cleaning method in anuclear generation station should reduce or eliminate radiation exposurecaused from opening the adsorption tower. Additionally, this cleaningmethod should prevent tritium releases to the atmosphere.

SUMMARY OF THE INVENTION

The present invention solves the aforementioned problems with the priorart as well as others by providing a method and apparatus for on-linecleaning of an adsorption tower having a plurality of distributorspositioned therein. A regulated supply of a high pressure fluid isemployed to generate a pressure pulse into the distributor fordislodging deposits blocking the openings therein.

In the preferred embodiment, an accumulator is filled with the fluid toa predetermined pressure, and then the fluid is released into thedistributor through a pressure conduit to cause the surge. The surge inpressure dislodges the deposits blocking the openings of thedistributor. In this fashion, the distributors may either be cleanedsingly in a sequential manner or simultaneously.

An object of the present invention is to provide an on-line cleaningmethod and apparatus for dislodging deposits in the distributors of anadsorption tower.

Another object of the present invention is to provide a method andapparatus for a sequential on-line cleaning of the distributors in anadsorption tower.

A further object of the present invention is to provide such a devicethat is simple in design, rugged in construction, and economical tomanufacture.

The various features of novelty which characterize the present inventionare pointed out with particularity in the claims annexed to and forminga part of this disclosure. For a better understanding of the invention,and the operating advantages attained by its uses, reference is made tothe accompanying drawings and descriptive matter in which a preferredembodiment of the invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a sectional schematic representation of an adsorption towerused in upgrading D₂ O for a nuclear power plant;

FIG. 2 is an elevational perspective view of the distributor;

FIG. 3 is a sectional schematic representation of an embodiment of thepresent invention;

FIG. 4 is a sectional schematic representation of an alternateembodiment of the present invention; and

FIG. 5 is a sectional schematic representation of still anotherembodiment of the present invention attached to a single distributor.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the figures, where identical numerals designate similar orlike features throughout the several views, there is shown an adsorptiontower (10) used in upgrading D₂ O for a nuclear power plant. Asexplained earlier, the impure deuterium oxide (D₂ O) enters theadsorption tower (10) from the top of the vessel with water (H₂ O) vaporentering at the upper side of the vessel. The D₂ O descends throughseveral distributors (12) positioned vertically within the tower (10).These devices are well known in this art and may be used to distill,refine, or separate various types of liquids. FIG. 1 depicts only oneapplication for an adsorption tower which is the upgrading of heavywater.

In the adsorption tower (10), the distributors (12) are devices similarto a large sprinkler having a plurality of holes or openings (14)situated on the bottom of tubes (16) which extend on both sides of thedistributor as shown in FIG. 2. Deposits are carried by the liquidentering the distributor (12) in the direction of the arrow causing ablockage of the openings (14) and the tube (16) of the distributor (12).The flow of the liquid through openings (14) are shown in dashed lines.

Referring to FIG. 3, there is shown one embodiment of the presentinvention attached to the distributors (12) of the adsorption tower(10). A regulated supply of a high pressure fluid (18) such as nitrogenfills an accumulator (20) to a predetermined pressure. Valve switch (24)actuates a high speed valve (22) either manually or automatically tocause a surge of nitrogen through a common manifold (28) into thepressure conduits or lines (26) into the distributors (12). The nitrogenrapidly expands in the liquid in the distributors (12) which causes apressure rise for dislodging any deposits blocking the openings (14).

Even though FIG. 3 shows a common manifold (28) with only one valve(22), it is apparent that each distributor can have its own valve (22)for a more selective control with the use of a computer ormicroprocessor (not shown). This allows the distributors to be cleanedinvididually when necessary, sequentially, or simultaneously on-linewithout disrupting the process underway in the tower.

An alternate embodiment includes the distributors (12) being connectedindividually to a single flexible line (28') as shown in FIG. 4. Thevalve switch (24) controls valve (22) either manually or automaticallywith the assistance of an optional computer. Preferably, quick connectcouplers (34) are employed and positioned outside the adsorption tower(10) to provide a means for quick connection to each distributor (12).After all of the distributors are cleaned, the device may be moved on tothe next adsorption tower or away from the surrounding area.Advantageously, a single device may be used to quickly clean severaltowers with little exposure to the hostile environment. Quick connectcouplers (34) are readily available for high pressure fluids. Thoseemployed for compressed air are suitable for the present invention.Either of the embodiments shown in FIGS. 3 and 4 can use these quickconnect couplers. The pressure conduits (26) may be fastened to thedistributors in any of several different manners to provide a pressuretight seal.

Experimental tests revealed that a pressure of 1000 psi in theaccumulator achieves a pressure rise of about 40 psi in a singledistributor which sufficiently cleans all of the 1/16 inch holes in a D₂O upgrader.

FIG. 5 depicts still another embodiment of the present invention whichutilizes the injection of a liquid at high velocity into the distributor(12). An external force indicated by the arrow may be used eithermanually or automatically to drive a piston (30) of a pump (32) having acavity of a predetermined volume and connected to a supply of fluid forinjecting the liquid through the pressure conduit (26) into thedistributor (12) at a very fast rate. This causes a pressure risethroughout the distributor of sufficient magnitude to clear the blockedopenings. Either of the embodiments in FIGS. 3 or 4 may be modified touse the injection of a liquid as shown in FIG. 5 rather than a gas.

A further embodiment of the present invention utilizes ultrasonictransducers positioned in each of the distributors. The ultrasonictransducers are then actuated by a microprocessor or computerperiodically to keep the holes clear.

While specific embodiments of the present invention have been shown anddescribed in detailed to illustrate the application and principles ofthe invention, it will be understood that it is not intended that thepresent invention be limited thereto and that the invention may beembodied otherwise without departing from such principles.

What is claimed is:
 1. An on-line method for cleaning an adsorptiontower having a plurality of distributors positioned therein with each ofthe distributors having a plurality of openings susceptible to blockage,comprising the steps of:providing a supply of a high pressure fluid;releasing a surge of the fluid from the supply with an accumulator andvalve switching means connected thereto into a conduit connected to eachof the distributors; passing the surge of fluid through the conduitdirectly into the distributors to cause a pressure rise therein; anddislodging deposits blocking the openings in each of the distributorswith the pressure rise of the fluid surging therethrough therebycleaning the adsorption tower.
 2. A method as recited in claim 1,further comprising the step of filling the accumulator with the fluid toa predetermined pressure.
 3. A method as recited in claim 2, wherein thefluid is nitrogen.
 4. method as recited in claim 2, wherein thereleasing step includes the step of releasing instantaneously the fluidfrom the accumulator into the distributors.
 5. A method as recited inclaim 1, wherein the predetermined pressure in the accumulator is about1000 psi.
 6. A method as recited in claim 1, wherein the releasing stepis sequentially performed in one distributor after another.
 7. A methodas recited in claim 1, wherein the releasing step is performedsimultaneously on all distributors.
 8. A method as recited in claim 1,wherein the fluid is a gas.